call 'rm' instead of '/bin/rm'
Fixed 'make clean' for several LaTeX results.

Wildcard expansion like 'rm -f foo.{ps,pdf}' works only when called from
a shell and not from Makefiles.
Typography fixes: \small, \verb, \mathit and \holtxt are now applied
consistently in DESCRIPTION, Section 1.5.

The rules are:
- \small is applied to \verb and \holtxt but not to math mode ($...$)
- \mathit is applied to all multichar symbols, e.g. "op", "thy", "const"
- there is no space around commas between functions arguments
Typography: "bool" and "num" subscripts are now horizontally aligned.
Typography: missing spaces added.
Consistent use of "failure" instead of "failure occurs".
Do not start a new paragraph in the middle of a sentence.
Missing space added.
Grammar error fixed.
Consistent use of semicolons instead of full stops in enumerations.
Extra space removed where two \index commands were surrounded by text.
Typos: one dot removed, other dot added.
Derived rules chapter: spacing fixed.
ML derived rules must be defined as 'fun' and not 'val'
Description: spacing fixed.
Typography: problematic macros marked with FIXME notes.
Typo: comma at the end of sentence.
Fixed 'make clean' for .ps and .pdf LaTeX outputs.

Wildcard expansion like 'rm -f foo.{ps,pdf}' works only in shell and not
in Makefiles.
Typography: extra space between '\index{...} \index{...}' removed.
Typography: correct spacing after i.e. and e.g.